1) Field of the Invention
The present invention relates to crosslinkable polymer compositions in the form of their aqueous polymer dispersions or polymer powders redispersible in water, processes for their preparation and their use.
2) Background Art
The preparation of polymers containing epoxy groups by copolymerization of monomers containing epoxy groups is known. WO-A 95/04767 describes a process for the preparation of aqueous polymer dispersions or polymer powders obtainable therefrom, in which a hydrophobic copolymer optionally substituted by epoxy groups is prepared in the presence of a low molecular weight water-soluble polymer substituted by carboxyl groups. WO-A 93/22353 discloses the preparation of polymers in the form of their aqueous polymer dispersions or polymer powders redispersible in water, vinyl esters of branched carboxylic acids having 11 to 15 C atoms being copolymerized, inter alia, also with comonomers having epoxide functional groups, such as glycidyl methacrylate. EP-A 721004 relates to crosslinkable polymer powders which are redispersible in water and which are composed of a film-forming polymer component having functional groups, such as hydroxyl groups, and a crosslinking component, for example epoxy resins.
Common to all these processes is the fact that the second reactive component is not mixed with the polymer dispersion or with the polymer powder until after the preparation of the crosslinkable polymer. Although precrosslinking can thus be prevented, only low degrees of crosslinking and inhomogeneous products result in the case of poorly compatible components.
It was thus the object to provide crosslinkable polymer compositions which have a long shelf life and form homogeneous films with a high degree of crosslinking.
The invention relates to crosslinkable polymer compositions in the form of their aqueous polymer dispersions or polymer powders redispersible in water, containing
A) a copolymer of one or more comonomers from the group consisting of vinyl esters of straight-chain or branched alkanecarboxylic acids having 1 to 18 C atoms, acrylates or methacrylates of branched or straight-chain alcohols having 1 to 15 C atoms, dienes, olefins, vinylaromatics and vinyl halides, and of from 0.1 to 10% by weight, based on the total weight of the comonomers, of one or more ethylenically unsaturated comonomers containing epoxide groups, and
B) one or more non-copolymerizable compounds having at least two epoxide groups.
The invention furthermore relates to a process for the preparation of crosslinkable polymer compositions in the form of their aqueous polymer dispersions or polymer powders redispersible in water by emulsion polymerization of one or more comonomers from the group consisting of vinyl esters of straight-chain or branched alkanecarboxylic acids having 1 to 18 C atoms, acrylates or methacrylates of branched or straight-chain alcohols having 1 to 15 C atoms, dienes, olefins, vinylaromatics and vinyl halides, and of from 0.1 to 10% by weight, based on the total weight of the comonomers, of one or more ethylenically unsaturated comonomers containing epoxide groups, and optionally drying of the resulting polymer dispersions in the presence of one or more protective colloids, one or more non-copolymerizable compounds having at least two epoxide groups being added before, during or after the emulsion polymerization.
Suitable vinyl esters are vinyl esters of straight-chain or branched carboxylic acids having 1 to 18 atoms. Preferred vinyl esters are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate and vinyl esters of xcex1-branched monocarboxylic acids having 9 to 11 C atoms, for example VeoVa9R or VeoVa10R (trade names of Shell). Vinyl acetate is particularly preferred.
Suitable monomers from the group consisting of the esters of acrylic acid or methacrylic acid are esters of straight-chain or branched alcohols having 1 to 15 C atoms. Preferred methacrylates or acrylates are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate and norbornyl acrylate. Methyl acrylate, methyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate and norbornyl acrylate are particularly preferred.
Suitable dienes are 1,3-butadiene and isoprene. Examples of copolymerizable olefins are ethene and propene. Vinylaromatics which can be polymerized are styrene and vinyltoluene. From the group consisting of the vinyl halides, vinyl chloride is usually used.
Optionally from 0.05 to 10% by weight, based on the total weight of the monomer mixture, of auxiliary monomers can also be copolymerized. Examples of auxiliary monomers are ethylenically unsaturated mono- and dicarboxylic acids, preferably acrylic acid, methacrylic acid, fumaric acid and maleic acid; ethylenically unsaturated carboxamides and carbo-nitriles, preferably acrylamide and acrylonitrile; mono- and diesters of fumaric acid and maleic acid, such as the diethyl and diisopropyl esters; and maleic anhydride; ethylenically unsaturated sulfonic acids and their salts, preferably vinylsulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid. Further examples are precrosslinked comonomers, such as polyethylenically unsaturated comonomers, for example divinyl adipate, diallyl maleate, allyl methacrylate or triallyl cyanurate, or postcrosslinked comonomers, for example acrylamidoglycolic acid (AGA), methyl methacrylamidoglycolate (MAGME), N-methylolacrylamide (NMA), N-methylolmethacrylamide, N-methylolallyl-carbamate, alkyl ethers, such as isobutoxy ether, or esters of N-methylolacrylamide, of N-methylolmethacrylamide and of N-methylolallylcarbamate. Further examples are comonomers having silicon functional groups, such as acryloyloxypropyltri(alkoxy)- and methacryloyloxypropyltri(alkoxy)silanes or vinyltrialkoxysilanes and vinylmethyldialkoxysilanes, it being possible, for example, for ethoxy and ethoxypropylene glycol ether radicals to be present as alkoxy groups.
Suitable comonomers containing epoxide groups are glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, vinyl glycidyl ether, vinylcyclohexene oxide, limonene oxide, myrcene oxide, caryophyllene oxide, styrenes and vinyltoluenes substituted by a glycidyl radical in the aromatic moiety and vinyl benzoates substituted by a glycidyl radical in the aromatic moiety. Glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether and vinyl glycidyl ether are preferred. Preferably, the amount of the comonomer units having epoxide functional groups is from 0.1 to 5.0% by weight, based on the total weight of the comonomers.
Most preferred are the copolymers mentioned below which also have the above-mentioned comonomer units containing epoxide groups, in the amounts described above. The data in % by weight and the amount of comonomer units containing epoxide groups sum in each case to 100% by weight.
From the group consisting of the vinyl ester polymers:
Vinyl acetate polymers;
vinyl ester/ethylene copolymers, such as vinyl acetate/ethylene copolymers, having an ethylene content of from 1 to 60% by weight;
vinyl esters/ethylene/vinyl chloride copolymers having an ethylene content of from 1 to 40% by weight and a vinyl chloride content of from 20 to 90% by weight, preferably vinyl acetate and/or vinyl propionate and/or one or more copolymerizable vinyl esters, such as vinyl laurate, vinyl pivalate, vinyl 2-ethylhexanoate, vinyl esters of an alpha-branched carboxylic acid, in particular vinyl versatate (VeoVa9R, VeoVa10R), being present as vinyl esters;
vinyl acetate copolymers with from 1 to 50% by weight of one or more copolymerizable vinyl esters, such as vinyl laurate, vinyl pivalate, vinyl 2-ethylhexanoate, vinyl esters of an alpha-branched carboxylic acid, in particular vinyl versatate (VeoVa9R, VeoVa10R), which optionally also contain from 1 to 40% by weight of ethylene;
vinyl ester/acrylate copolymers containing from 30 to 90% by weight of vinyl esters, in particular vinyl acetate, and from 1 to 60% by weight of acrylates, in particular n-butyl acrylate or 2-ethylhexyl acrylate, which optionally also contain from 1 to 40% by weight of ethylene;
vinyl ester/acrylate copolymers containing from 30 to 75% by weight of vinyl acetate, from 1 to 30% by weight of vinyl laurate or vinyl esters of an alpha-branched carboxylic acid, in particular vinyl versatate, and from 1 to 30% by weight of acrylates, in particular n-butyl acrylate or 2-ethylhexyl acrylate, which optionally also contains from 1 to 40% by weight of ethylene.
From the group consisting of the (meth)acrylate polymers:
Copolymers containing n-butyl acrylate and/or 2-ethylhexyl acrylate; copolymers of methyl methacrylate with n-butyl acrylate and/or 2-ethylhexyl acrylate and/or 1,3-butadiene.
From the group consisting of the vinyl chloride polymers, vinyl chloride/ethylene copolymers and vinyl chloride/acrylate copolymers in addition to the above-mentioned vinyl ester/vinyl chloride/ethylene copolymers.
From the group consisting of the styrene polymers, styrene/1,3-butadiene copolymers and styrene/acrylate copolymers, such as styrene/n-butyl acrylate or styrene/2-ethylhexyl acrylate having a styrene content of, in each case, from 1 to 70% by weight.
The epoxide compounds which are not capable of free radical polymerization and have at least two epoxide groups per molecule may be aliphatic, araliphatic or aromatic. Suitable non-copolymerizable compounds having at least two epoxide groups are, for example, those of the bisphenol A type, i.e. condensates of bisphenol A and epichlorohydrin or methylepichlorohydrin. Such epoxide crosslinking agents are commercially available, for example, under the trade names Epicote and Eurepox. Epoxy resins based on bisphenol F, which generally contain a mixture of bisglycidyloxyphenylmethanes, are also suitable. Further examples are aliphatic epoxide compounds, such as glycidyl ethers of aliphatic polyols, in particular butyl diglycidyl ether; cycloaliphatic epoxy resins, such as vinylcyclohexane dioxide, dicylcopentadiene dioxide and 3,4-epoxy-6-methylcyclohexylmethyl; and heterocyclic epoxide compounds, such as triglycidyl isocyanurate.
The epoxide compounds of the bisphenol A type, i.e. condensates of bisphenol A and epichlorohydrin or methylepichlorohydrin, are preferred. The epoxide compounds are present in the polymer composition in an amount of from 1 to 50% by weight, preferably from 1 to 15% by weight, based in each case on the total weight of copolymer A) and epoxide compound B).
The copolymers are prepared by the emulsion polymerization process. This is carried out in an open reaction vessel or in pressure-resistant vessels in a temperature range from 0xc2x0 C. to 100xc2x0 C. and is initiated by the methods usually used for emulsion polymerization. The initiation is effected by means of the conventional free radical formers, at least some of which are water-soluble and which are used preferably in amounts from 0.01 to 3.0% by weight, based on the total weight of the monomers. Examples of these are sodium persulfate, hydrogen peroxide, tert-butyl peroxide, tert-butyl hydroperoxide; potassium peroxodiphosphate and azobisisobutyronitrile. If required, said free radical initiators can also be combined in a known manner with from 0.01 to 0.5% by weight, based on the total weight of the monomers, of reducing agents. For example, alkali metal formaldehyde sulfoxylates and ascorbic acid are suitable. In the case of the redox initiation, one or both redox catalyst components are preferably metered during the polymerization.
All emulsifiers usually used in emulsion polymerization may be employed as dispersants. Suitable emulsifiers are anionic, cationic and nonionic emulsifiers. Preferably, the emulsifiers are used in an amount of up to 3% by weight based on the total weight of the monomers. For example, anionic surfactants, such as alkylsulfates having a chain length of 8 to 18 C atoms, alkyl and alkylaryl ether sulfates having 8 to 18 C atoms in the hydrophobic radical and up to 40 ethylene oxide or propylene oxide units, alkanesulfonates or alkylarylsulfonates having 8 to 18 C atoms and esters and monoesters of sulfosuccinic acid with monohydric alcohols or alkylphenols are suitable. Suitable nonionic surfactants are, for example, alkyl polyglycol ethers or alkylaryl polyglycol ethers having 8 to 40 ethylene oxide units.
The preparation is preferably carried out in the presence of protective colloids. Examples of suitable protective colloids are polyvinyl alcohols containing from 75 to 100 mol %, preferably from 78 to 95 mol %, of vinyl alcohol units and having a molecular weight of, preferably, from 5000 to 200,000; polyvinylpyrrolidones having a molecular weight of from 5000 to 400,000; polysaccharides in water-soluble form, such as starches (amylose and amylopectin), celluloses and their carboxymethyl, methyl, hydroxyethyl and hydroxypropyl derivatives, preferably hydroxyethyl-celluloses having a degree of substitution of from 1.5 to 3; proteins, such as casein, soybean protein and gelatin; ligninsulfonates, synthetic polymers, such as poly(meth)acrylic acid, poly(meth)acrylamide, polyvinylsulfonic acids and their water-soluble copolymers; melamine formaldehyde sulfonates, naphthalene formaldehyde sulfonates and styrene/maleic acid and vinyl ether/maleic acid copolymers.
The pH range desired for the polymerization, which is generally between 2.5 and 10, preferably between 3 and 8, can be established in a known manner by means of acids, bases and conventional buffer salts, such as alkali metal phosphates or alkali metal carbonates. For establishing the molecular weight, the regulators usually used, for example mercaptans, aldehydes and chlorohydrocarbons, may be used in the polymerization.
Regardless of the polymerization process chosen, the polymerization can be carried out batchwise or continuously, with or without the use of seed latices, initially introducing all or individual components of the reaction mixture, or initially introducing some of them and subsequently metering the or individual components of the reaction mixture, or by the metering method without initial introduction. The epoxide compounds B) not capable of free radical polymerization can be added before, during or after the polymerization of the copolymer A). In the preparation of pulverulent polymer compositions, for example, addition may also be effected during or after the drying of the corresponding polymer dispersion.
In preferred embodiments, the comonomer having epoxide functional groups and the non-copolymerizable epoxide compounds are added before or shortly after the start of the polymerization. It is also preferable if the comonomer having epoxide functional groups is added before or shortly after the start of the reaction while the non-copolymerizable epoxide compound is metered in with the final 5 to 40% by weight of the remaining comonomers. A further preferred embodiment comprises metering in both the comonomer having epoxide functional groups and the non-copolymerizable epoxide compound with the final 5 to 40% by weight of the remaining comonomers. Said variants lead to polymer compositions which, during use, are distinguished in particular by outstanding solvent resistance and lead to polymer compositions which, when used, give water-resistant films.
The solids content of the dispersion thus obtainable is from 20 to 70%. The mean particle size is from 0.1 to 10 mm,. preferably from 0.2 to 5 mm.
The drying of the dispersion can be effected by means of spray-drying, freeze-drying or fluidized-bed drying. Spray-drying in conventional spray-drying units is preferred, it being possible to effect atomization by means of airless high-pressure nozzles, binary nozzles or multi-material nozzles or by means of a rotating disk. The outlet temperature is chosen in general in the range from 55xc2x0 C. to 100xc2x0 C., preferably from 65xc2x0 C. to 90xc2x0 C., depending on the unit, Tg of the resin and the desired degree of drying.
For spray-drying, the dispersion of the copolymer A) having a solids content of preferably from 20% to 60% is sprayed and dried together with protective colloids as a spraying assistant. Protective colloids which may be used are the above-mentioned ones, it being possible to add the protective colloids to the aqueous dispersion before the spray-drying, in the form of an aqueous solution. In this process step, from 5 to 20% by weight of protective colloid, based on copolymer A), are preferably added.
Optionally, the powder composition may also be modified with further additives. Examples of these are antiblocking agents, dyes, pigments, plasticizers, film formation assistants, antifoams, catalysts, rheology assistants, thickeners, adhesion promoters and emulsifiers, it being necessary to convert them, if they are liquid in the original state, into a pulverulent state prior to admixing.
The dispersion powder composition can be used in the applications typical for them, for example in chemical products for the construction industry in conjunction with inorganic, hydraulically setting binders, such as cements (Portland, alumina, trass, slag, magnesia or phosphate cement), gypsum, waterglass, for the production of construction adhesives, renders, filling compounds, floor filling compounds, joint mortars and paints, and furthermore as sole binders for coating compositions, for example emulsion paints and powder coatings, and as sole binders in adhesives, for example for wood, board, paper and fiber materials, in particular in wood adhesives, parquet adhesives, packaging adhesives and bookbinding adhesives. A further use is as a binder for textiles and paper.
For these applications, the dispersions or powders can be modified with the corresponding additives. Suitable additives are fillers, such as chalk or gypsum. Wetting agents, dispersants, thickeners, antifoams and/or preservatives may furthermore be added.
The Examples below serve for further explanation of the invention: